I wouldn't use it personally. For us, it was enabled as part of an update -- I can't remember whether it was automatic or asked.

Unfortunately with the new IMAPd we experience:

phantom messages in the Inbox, with no subject and no body. They disappear when clicked on, but always come back on the next IMAP check

deleting/moving a message using IMAP does not update the ActiveSync device. If the message isn't deleted/moved on a mobile then it might as well not have happened, even though the mailbox appears to have been updated on the IMAP client.

The IMAP client in this case is Apple Mail, and the ActiveSync is a wide variety, from iOS to Blackberry Android.